IMO the best (unmodded) animal for your meat industry is rocs, because in addition to being friggin huge their meat is also very valuable, which is passed on to the roasts you make with them. Though they lay small clutches, they also grow to adulthood ridiculously fast.
Yes, apparently they do have CHILD:1, but this is only a tag for sexual maturity. Their size/growth tags are [BODY_SIZE:0:0:200000], [BODY_SIZE:1:0:5000000], and [BODY_SIZE:20:0:20000000]. For comparison, 200k is an adult grizzly, 5 million is an adult elephant and the only things 20 million or larger are bronze colossuses (20 million), fully grown dragons (25 million), whale sharks (20 million), giant orcas (20 million), Giant Elephant seals (24.12 million), Sperm whales (25 million), and Giant sperm whales (100 million). Ok so yea, Rocs are pretty amazing, if you butcher them as soon as they're adolescents (since that's when their growth slows down), largely thanks to the x15 value multiplier, which is only shared by dragons. But dragons grow at a steady pace from 6k at hatching to 25 million at 1000 years old, which comes to a rate of about 25k a year. That's some growth spurt on the rocs' part.
But cave crocs are still one of the best options. 20-60 eggs per clutch, x4 value multiplier, 600k (cow-sized) adults at 2 years, or half that at 1 year. Comparing total volumes for a rough comparison of butchering returns, 20*300k cave crocs is 12 million cm
3, so if it weren't for the huge value multiplier on the rocs, crocs would be pretty competitive when it comes to actual amounts of meat, because rocs only lay clutches of 1-2.
Saltwater crocodiles "only" have a value multiplier of x3 and are more restricted in biomes, but grow to 800k in 2 years (again, half that at 1 year) and lay clutches of 20-70 eggs.
With enough patience to amass a larger breeding population of females, rocs outstrip crocs even more because with crocs, you hit the species pop cap pretty quickly, but with rocs you could be raising a 20-30 of them per year after a few years. And crashing the global economy with your high-value food exports.